1. Field of the Invention
The present invention is generally related to the inspection of equipment and particularly to the inspection of equipment not readily accessible to conventional measurement or inspection techniques.
2. General Background
In industrial environments, particularly the nuclear industry, certain equipment is not readily accessible for inspection or damage assessment either due to the physical location of the equipment or the fact that it is radioactive. Patents directed to remote inspection techniques that applicants are aware of include the following.
U.S. Pat. No. 4,303,608 discloses an apparatus for replicating the submerged surfaces of ships. A housing is sealingly engaged with the ship surface. Water is evacuated from the molding region between the ship and the housing. Molding material is forced into the molding region and the device is held in position until the material solidifies.
U.S. Pat. No. 4,198,362 discloses a device where wax or other molding material is caused to contact a surface. A heating element imbedded in the molding material is then used to soften the molding material so that an impression of the surface can be made.
U.S. Pat. No. 3,966,871 is directed to the inspection of internal tubular cavities. An elastically hardenable plastic is cast against the surface and after hardening is pulled from the tubular cavity for inspection.
U.S. Pat. No. 3,995,483 discloses the use of a penetrating liquid dye that is particularly applicable to hot surfaces for making surface defects visible.
U.S. Pat. No. 2,601,703 discloses a method of testing for surface defects where a negative hard plastic cast of the machine elements are made for inspection.
In the nuclear industry, the nature of the equipment and the presence of radioactivity precludes the disassembly of equipment during routine shutdowns for scheduled maintenance and inspection. The control rod drive mechanism (CRDM) of nuclear reactors is subject to steam cut damage on the nozzle flanges and must be inspected on a periodic basis. Video inspection of this equipment provides only gross measurement. The use of liquid penetrant dye subjects personnel to radiation exposure. Precise dimension inspection tools are complex, expensive, require periodic calibration, and the accuracy is often subject to operator skill.